Chassis for conventional information and communications technology (ICT) systems include linecards which typically have separate modules enabled by an optical interface. The modules can be optically interconnected to establish an ultra-high speed data exchange link. Light source provisioning for the optical channels on a linecard is enabled by external laser arrays via an optical frontplate. The frontplate is equipped with optical I/O (input/output) ports for aggregated optical channels. Each linecard is inserted into an electrical backplane to access the backplane low-speed control unit, power management and power supply. High speed data transmission is enabled via the optical frontplate. The optical I/O channels from the frontplate can be connected, via a fiber cable, to another linecard in the same chassis, or connected to an optical cross connect (OXC) unit in the chassis. Additional ports in the OXC units can establish inter-chassis optical interconnects. Based on the system link requirements, the optical I/O channels should be designed to interconnect at various hierarchy levels such as module to module on the same linecard, linecard to linecard in the same chassis, linecard to OXC (optical cross-connect unit) to linecard in the same chassis, and chassis to chassis. The reach range can vary from millimeter (mm) to kilometer (km).
With regard to system cost, power consumption and scalability consideration, the use of optical amplifiers in such systems is preferably minimized. Consequently, the optical link power budget is a factor that depends on each specific interconnection requirement, which is typically limited by fiber and waveguide propagation loss, photonics device insertion losses such as couplers and modulators, as well as additional losses in intermediate routers and switches. Typically, a longer reach link with more photonics devices has higher optical loss and requires a higher link budget.
Silicon photonic based optical interconnects offer various advantages for ICT systems. However, thermal issues on high density linecards are a major concern for the monolithic integration of electronics and photonics. From a system deployment and maintenance perspective, efficient equipment installation procedure, device replacement and redundancy requirements favor external laser arrays as the light source provision solution. Furthermore, due to propagation and insertion loss induced by the optical fibers, waveguides, and other passive and active photonics devices, the optical link budget for different types of interconnects can vary from 0 to 30 dB. It is neither necessary nor cost effective to use excessive high power light sources for very short links. On the other hand, the minimum power budget should be met for each link. It is preferable to use standard integrated laser arrays for diverse optical interconnects scenarios to achieve a power efficient and cost effective solution.
Standard integrated laser arrays can meet the needs of diverse optical interconnect scenarios. However using homogenous laser arrays with the same wavelength requires a large number of optical fibers and connectors for light provision and interconnects. Another constraint in such systems is that the switches/routers can only be realized with a mesh topology network or active optical switching devices. Consequently, component count, installation/maintenance cost, and power consumption scale with the number of interconnected modules and linecards which becomes problematic for high capacity systems. Therefore a reach-adaptive power provision solution is desirable which uses standard integrated laser arrays in ICT systems.